The Radioimmunoassay (RIA) Core provides valuable radioimmunoassay services to HPC associates conducting research on basic biology, and on population-based reproductive function and behaviors. In addition to providing assay services for a large scale epidemiologic studies, the Core provides assay services to HPC scientists performing basic research in reproduction. For example, Core facilities were made available to perform steroid and prostaglandin assays on perfusate samples taken during experiments designed to elucidate biologic processes involved in ovulation. More recently, assay services have been provided for basic research studies investigating the interaction between the environment and reproductive behaviors. The following standard peptide, steroid and prostaglandin assays are available within the RIA Core laboratory: 1. Rat Pituitary Peptide Assay LH, FSH, PRL, TSH, GH 2. Human Pituitary Peptide Assays LH, FSH, PRL, TSH 3. Steroid Assays progesterone, estradiol, 17-OH progesterone, testosterone 4. Urinary Steroid Glucuronide Assays 5. Prostaglandin assays PGE2 and PGF2(alpha) The following Specialized Assays are also available: 1. Norethindrone and ethinyl estradiol 2. CA 125 3. Urinary hCG